Land vehicles are equipped with luminous devices, in particular lighting and/or signalling devices, such as headlamps or rear lights, that are intended to illuminate the road in front of the vehicle at night or in case of low visibility. They may also serve to illuminate the passenger compartment of the vehicle. These luminous devices may comprise one or more luminous modules. Each lighting function may be performed by one or more modules.
In these luminous land-vehicle modules, electroluminescent light sources are more and more frequently used. These light sources may consist of light-emitting diodes or LEDs, of organic light-emitting diodes or OLEDs, or even of polymer light-emitting diodes or PLEDs.
Solid-state monolithic light sources (also known as monolithic arrays of LEDs) have been known about for a short while. Monolithic light sources comprise tens, hundreds, or even thousands of LEDs that are located on the same substrate, the LEDs being separated from the others by lanes or streets. In this monolithic-array context the LEDs are also called pixels. These light sources are said to be of high LED density because the number of pixels is great, for example several hundred LEDs per cm2. Each of the LEDs is electrically independent from the others and therefore illuminates autonomously from the other LEDs of the array. Thus, each LED of the array is individually controlled by the electronic circuit (called the driver) that manages its electrical power supply.
Solid-state monolithic light sources have many advantages. They firstly deliver a high light intensity, this making it possible to improve the illumination of the scene and thus for example to make driving a motor vehicle safer. In addition, they create a highly pixelized light beam that allows existing driver-assist functionalities and in particular adaptive lighting functions to be implemented and improved. For example, an anti-glare function may be configured so that only the windshield of an oncoming vehicle is no longer illuminated.
Solid-state monolithic light sources however have drawbacks. Firstly, these light sources heat and require a specific management of the heat generated by the electroluminescent elements. Specifically, the generated heat leads to an increase in the temperature of components, which may degrade these components and/or prevent optimal use thereof. In addition, these light sources suffer from crosstalk, i.e. the light emitted by an electroluminescent element interferes at least with the light emitted by the neighbouring electroluminescent elements. The pixelization of the light beam emitted by the source is therefore affected. Furthermore, some of the light emitted is lost because all the emitted light cannot be collected because of the angle of emission of the electroluminescent elements, which is large. Lastly, another problem is that the lanes or streets present on the source cause intervals to appear between the various light beams from which the beam of the source is composed. The light beam obtained as output is therefore not a uniform light beam. In addition, these lanes or streets form non-emissive zones that cause the average luminance of the source to drop below the value of the luminance of the emitter. This loss may be very great; for example, if the pitch is 50 μm and the emitters are of 40 μm, the non-emissive area is about 36% of the total area of the source.